Crystal and molecular structures of eight-coordinate (CuN4O4) and six-coordinate (CuN4O2) Cu(II) complexes with 4-methyl-5-imidazole-carboxaldehyde or 1-benzyl-2-hydroxymethylimidazole, respectively: Spectroscopic and potentiometric studies

The synthesis and characterisation of two novel Cu(II) eight and six coordinate compounds with the bidentate ligands 4-methyl-5-imidazolecarboxaldehyde (4-Me-5-CHOIm) and 1-benzyl-2-hydroxymethylimidazole (1-Bz-2-CH₂OHIm) are described. Single crystals of Cu(4-Me-5-CHOIm)₄](H₂O)₂(NO₃)₂ (1) and Cu(1-Bz-2-CH₂OHIm)₄](NO₃)₂ (2) were used in structure determinations. The two compounds both crystallise in the monoclinic space group P with Z=2 for (1) and Z=1 for (2). The structural data for (1) indicated that Cu(II) ion is involved in a flattened tetrahedron of N(1), N(2), N(3) and N(4) atoms of imidazoles ring as well as in a more distant elongated tetrahedron of four of the z-axis oxygen atoms O(1), O(2), O(3), O(4) of aldehyde groups. The coordination scheme of the six-coordinate Cu(II) complex (2) is a slightly distorted tetragonal bipyramid and the ligands act as a monodentate and bidentate. Additionally, the coordination processes with Cu(II) were detected and characterised in solution using spectroscopic (EPR and UV–VIS) as wall as potentiometric methods.